The invention relates to an exhaust system of an internal-combustion engine having a movable catalyst which is arranged to be moved into and out of an exhaust pipe of the engine.
When a catalyst is to be used for purifying the exhaust gas flow of an internal-combustion engine, this catalyst must meet two requirements: fast heating and resistant to overheating. The simultaneous meeting of these requirements makes it necessary that special measures be taken. After the start of its operation, the catalyst must be very rapidly brought to such a high temperature that it can be used for purifying the exhaust gas. For this purpose, a small catalyst is optimally suitable and is installed in the exhaust pipe as closely as possible to the internal-combustion engine. In order to avoid overheating of the small catalyst during high engine performance and correspondingly large and hot exhaust gas flow and to prevent destruction by overheating, the exhaust gases can be guided around the catalyst in a bypass pipe (see U.S. Pat. No. 3,972,184). Flaps are used for controlling the bypass pipe. Here the exhaust gas flow is diverted. This results in an additional loss of pressure and an overheating of the catalyst is not rendered impossible.
An object of the instant invention is to provide an exhaust system for an internal-combustion engine which is safe in its operation and has a low exhaust gas back pressure.
This object is achieved by having the catalyst movably disposed at the exhaust pipe in such a manner that it can at least be moved partially out of the exhaust gas flow current in the exhaust pipe. If the small catalyst serving as the starting catalyst is movably disposed in the exhaust gas pipe and can be moved out of the exhaust gas flow into a lateral chamber of the exhaust gas pipe, overheating can be avoided without the requirement of a bypass pipe and control flaps. After the catalyst is removed from the exhaust gas flow in the exhaust, a smooth passage opening is available to this flow which ensures a low loss of pressure of this flow.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.